flipper

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A wide flat limb, as of a seal, whale, or other aquatic mammal, adapted for swimming.
2. n. A rubber covering for the foot having a flat flexible portion that widens as it extends forward from the toes, used in swimming and diving. Also called fin¹.
3. n. A flat lever in a pinball machine, used to hit the ball so it stays in play.

Century Dictionary and Cyclopedia

1. n. A limb used to swim with. The fin of a fish.
2. n. The hand: as, give us your flipper.
3. n. Part of a scene, hinged and painted on both sides, used in trick changes.
4. n. A flapjack; a kind of griddle-cake.
5. n. In a sawmill, a steam-operated device for flipping, upsetting, or throwing over a log, cant, or piece of timber from a set of live rolls to other rolls, or for throwing a log out of the log-slide to the log-deck preparatory to rolling it down the sloping deck to the log-loader.

Wiktionary

1. n. in marine mammals such as whales, a wide flat limb, adapted for swimming
2. n. a flat, wide, paddle-like rubber covering for the foot, used in swimming
3. n. a flat lever in a pinball machine, used to keep the ball in play
4. n. cricket A type of ball bowled by a leg spin bowler, which spins backwards and skids off the pitch with a low bounce
5. n. informal, US television remote control, clicker
6. n. dated, slang The hand.
7. n. dentistry A kind of false tooth, usually temporary.
8. v. To lift one or both flipper out of the water and slap the surface of the water

GNU Webster's 1913

1. n. (Zoöl.) A broad flat limb used for swimming, as those of seals, sea turtles, whales, etc.
2. n. (Naut.), Slang The hand.

WordNet 3.0

1. n. a shoe for swimming; the paddle-like front is an aid in swimming (especially underwater)
2. n. the flat broad limb of aquatic animals specialized for swimming